Answer:
r =

Explanation:
Multiply both sides by r + 120.
t (r + 120) = 120r
Expand.
tr + 120t = 120r
Subtract tr from both sides.
120t = 120r - tr
Factor out the common term r.
120t = r (120-t)
Divide both sides by 120 - t.
= r
Finally, switch r to the left side and you get your answer.
//also, sorry for answering late.. my wifi is poopy//